If she has taken two pregnancy tests, and they were both negative, then the chances are VERY slim that she's pregnant. Sperm can't survive very long outside of the body, and the fact that you washed it off makes the chanes a lot less. Now, since this is the second time you've been concerned about it, I highly recommend that you two look into birth control options. If she needs parent approval to get it (which in my province, once you're 16 you don't) then she can just say it's for her period.

“You are braver than you believe,
stronger than you seem,
and smarter than you think.”